First-Principles Study on Mg/NbB2 Heterogeneous Nucleation Interface

Using first-principles method based on density functional theory, the interfacial adhesion, stability and bonding nature of Mg (0001)/NbB2 (0001) interface were studied to analyze the heterogeneous nucleation potency of primary alpha-Mg grains on NbB2 particles. The results indicated that B-terminated-hollow-site (Mg atom residing on top of the second layer of NbB2 slab) interface with the largest work of adhesion and smallest interfacial energy is the most stable among six different interfaces. Moreover, the interfacial energy is lower than that of alpha-Mg/Mg melt, 0.1 J/m(2). Besides that, the difference charge density and partial density of states indicated that the electronic structure of B-terminated interface with hollow-site stacking correspond to covalency, while that of Nb-terminated one correspond to metallicity. As a result, the relatively stable B-terminated interface with hollow-site stacking is conducive to the stacking of alpha-Mg on the NbB2 substrate and NbB2 particles are effective heterogeneous nucleation substrates for the nucleation and growth of Mg grains from crystallography and thermodynamics.